Multiple-Winding Motor Drive Control for Harmonic Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing drive control systems for multiple-winding motors face challenges in reducing harmonics and achieving accurate voltage phase and amplitude balance, especially with high-voltage large-capacity inverters that have slow switching devices, leading to instability and torque ripple due to magnetic coupling between windings.
Innovation Solution
A drive control apparatus that includes power converters and a control unit with an output voltage control unit, a PWM control unit, and a modulation rate phase command generation unit, which calculates and generates modulation rate and phase commands to equalize currents across windings, utilizing a pattern table for reducing low-order harmonics and adjusting control frequency based on the number of pulses and modulation rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-voltage large-capacity inverters with slow switching devices are used, then the inverter capacity is increased, but the switching speed decreases and low-order harmonics remain in output voltage
Solution Approach 1:
The patent applies parameter changes by modifying the PWM control parameters specifically for high-power inverters. It changes the carrier wave frequency and PWM switching strategy to accommodate slow switching devices while maintaining output quality. The control unit adjusts modulation depth and switching patterns to reduce low-order harmonics despite the limited switching speed of large-capacity inverters.
2Manufacturing precision
If triangular wave comparison PWM voltage control is used to eliminate current amplitude and phase differences, then current balance is improved, but very fast response is required which is difficult to achieve with high-voltage large-capacity inverters
Solution Approach 1:
The patent implements dynamics by making the control frequency adaptive. It dynamically adjusts the control frequency based on the actual switching capabilities of the inverter devices. The system transitions from fixed high-frequency triangular wave comparison to a flexible frequency approach that matches the physical constraints of the hardware, enabling current balance correction without requiring unrealistic response speeds.
Solution Approach 2:
The control unit changes the PWM control parameters including carrier frequency and modulation index based on the inverter's switching capabilities. For high-voltage large-capacity inverters, it uses lower carrier frequencies that are achievable with slow switching devices while still maintaining effective current balance through adjusted modulation strategies.
3Object-generated harmful factors
If control is performed with response faster than fundamental wave to reduce harmonics, then harmonic reduction is improved, but the PWM waveform symmetry is deformed and control stability decreases
Solution Approach 1:
The patent applies periodic action by using controlled PWM switching at specific frequencies that are synchronized with the fundamental wave. Instead of continuous high-speed switching that deforms waveforms, it uses periodic switching patterns at lower frequencies that maintain PWM waveform symmetry. The switching occurs at predetermined intervals that preserve the horizontal and vertical symmetry of the PWM waveform, ensuring control stability while still reducing harmonics.
Data Source
AI summary
A drive control apparatus for multiple-winding motor includes: a modulation rate phase command generation unit which calculates currents of first and second inverters for driving a multiple-winding three-phase motor and generates a modulation rate command and a phase command for equalizing the currents; a pulse number determination unit which determines the number of pulses per half cycle on the basis of a frequency command; a pattern table for storing switching patterns; and gate signal generators which control the first and second inverters, using an optimal switching pattern based on the number of pulses, wherein the modulation rate phase command generation unit performs control for equalizing currents of the first and second inverters, and the phase or frequency at which the control is performed is changed in accordance with any of the number of pulses, the modulation rate, the frequency command, and the switching pattern.